\usepackage {pstcol,pst-text}
\begin{pspicture}(-4,-3.2)(3,0.2)
 \psset{linecolor=lightgray}
 \pstextpath
  {\pscurve(-4,-2)(-2,0)(0,-3)(2,-1)(3,-2)}
  {\color{blue}
  If you want to type
  $3 \int^x_y = \sum^{n=1}_{33}$
  and let it follow along a
  curving line  \ldots}
\end{pspicture}
